Add support for clusters with a disabled config db

[gm42]

What would you like to be added/changed?

A FoundationDB cluster can be run with the config db disabled (--no-config-db passed to fdbserver processes); however when operator would issue the coordinators command via fdbcli, this is expected to result in a hanging command (for reference, see apple/foundationdb@cd2bbff and apple/foundationdb@1a33515).

The enhancement request is to allow in some way to run clusters with the config db disabled; this originally came up while discussing mitigations for N2_ConnectError to ghost coordinator IPs, see this forum thread.

[sfc-gh-ljoswiak]

I submitted apple/foundationdb#11491 to fix the client-side hang issue. This will remove the need to specify any extra flags on clients when the configuration database is disabled server side.